Question

A: Diver dives in and reaches a depth of 100m.
B: Diver swims up from the depth of 100m to the surface.
Choose the correct alternative:

• A. A is easier than B
• B. B is easier than A
• C. A and B are equally hard
• D. A is easier than B if speed of descent and ascent is same and more.

Answer 1

The correct option is A A is easier than B

Assume:

$F_d:\text{Force applied by diver during descent in downward direction}$

$F_u:\text{Force applied by diver during ascent in upward direction}$

$U:\text{Upthrust}$

$m:\text{Mass of the diver}$

$g:\text{Acceleration due to gravity}$

Uniform ascent and descent.

Diver has more density than water. Hence, weight of diver is more than the upthrust and without any effort, the diver sinks.

i.e. $mg>U..................\left(1\right)$

During upward motion, $F_u+U-mg=\mathrm{0............}\left(2\right)$

During downward motion, $F_d-U+mg=\mathrm{0...............}\left(3\right)$

From (1),(2) and (3),

$F_u-F_d=2mg-2U$

$F_u-F_d>0$

$F_u>F_d$